Thin section electron microscopy, EM cytochemistry, and freeze-etching techniques will be used to investigate the membranes of slime molds. The objective is to learn how the cell surface changes to enable cells to fuse, recognize self and non-self, phagocytize each other, and become contact inhibited. Intramembrane particles in the plasma membrane will be measured and characterized, and attempts made at isolation identification. Mechanical and chemical alteration of the cell membrane will be attempted in order to induce cell fusion in incompatible cells. Slime molds are being used because of their ease of handling compared to mammalian cells, but it is expected that the information will be applicable to mammalian cells as well. A freeze-fracture study of rat liver tumors is also being initiated in order to examine cell-to-cell contracts and find out how they change with transformation to the neoplastic state.